Feet or ball position on out of play

[eherrman]

Right fielder chases a foul ball toward the out of play line. He makes the catch right at the line at full sprint. Without instant replay it is near impossible to determine. It looked like the ball was over the line, but one foot may have still been on the playing field.

First base umpire signals "catch" and out. Home plate umpire overrules and calls ball out of play.

What is the appropriate ruling and who makes the call?